in no load tests we are using low power factor wattmeters and in blocked rotor tests we are preferring unity power factor wattmeters could anyone justify reason....
- posted
16 years ago
in no load tests we are using low power factor wattmeters ....y?
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- posted
16 years ago
------------------ Normal wattmeters will read full scale at rated current and voltage at unity pf. They will be adequate for locked rotor tests. However, at no load, the pf may be so low that readings are at the bottom end of the range and aren't very accurate. A low pf meter is one that would reach ful scale at rated voltage and current at a pf of , for example, 0.5.
This is more of a problem with transformers than with motors and simply may be a carryover of a practice used for transformers (open circuit tests).